Digital inkjet printing of signs and other graphic arts applications is increasingly replacing screen printing and other analog printing technologies. Digital inks for large format printing provide good image quality, durability, and permanence. While many of the inks in use are solvent-based, in recent years efforts have been made to replace solvent-based inks with water-based inks. Many of the media substrates are nonporous coated papers or polymer films such as vinyl.
Durability of aqueous inks on nonporous media poses a challenge. An ink typically needs to wet and adhere to a broad range of substrates, have good abrasion and scratch resistance, resist attack by water, cleaning fluids, and solvents, and have good outdoor weatherability. There have been great improvements in the durability of aqueous inkjet inks through incorporation of certain inkjet compatible latex polymer dispersions made by emulsion polymerization. When printed as part of an inkjet ink, a latex component of the ink can form a film on a media surface, entrapping and protecting the colorant within the hydrophobic print film.
This being said, while latex particulates can improve durability of prints, they undergo severe thermal shear conditions when printed through thermal inkjet print heads, leading to nozzle reliability issues. Moreover, those polymers tend to settle out of inks over time and, therefore, often are not stable in many storage conditions. Thus, there is a continuing need to provide latex particulates having improved stability and durability for printing on a wide variety of media types and with a variety of printing architectures.